I needed to back up my plugins to install the DOM inspector, which requires a firefox reinstall. Here is how to back up the firefox plugins:
C:\Documents & Settings\USERNAME\Application Data\Mozilla\Firefox\Profiles\
there are directories in there
copy those out to save them
then.... after you reinstall, copy them back and run "firefox -profilemanager"
and create a "NEW" profile using the directory you just copied
It works cross platform also... put the stuff on a jumpdrive and have the same profile in Linux and Windows